Canna lilies (Canna X generalis) have foliage that resembles banana leaves and large colorful flowers that bloom each year. Canna lilies--also known as just cannas--have fleshy root structures called rhizomes. They are hardy in USDA zones 8 to 12; however, in slightly colder zones, a couple inches of mulch may be sufficient to keep the rhizomes warm during the winter. In cold zones (5 and below), they must be dug up and stored during the colder months to survive.
Cut off the foliage after the first killing frost; it will be brown or yellow. Use sharp pruning shears or clips and leave about 4 to 6 inches of foliage above the ground.
Take a garden fork and start to dig a couple inches from the stem. Dig a complete circle around your plant, about 6 inches deep.
Push down on the gardens fork's handle. Repeat in several spots around the plant to lift the rhizome out of the soil. Remove some of the soil with your hands, but leave some on. Do not wash the rhizomes.
Dry the dug-up rhizomes in a cool dry location. Lay them out on an elevated screen or on some newspaper for a few hours to dry. This should be in a safe place, out of reach of children and animals. Do not dry them in the sun.
Store the rhizomes until spring in an open container or mesh bag in a location that is dry and between 40 to 50 degrees F. Attics, crawl spaces, basements and attics often make ideal storage locations.